Conventionally, a straddle vehicle such as a motorcycle is provided with an engine and a transmission which are integrated and has a structure to lubricate a transmission gear train using engine oil. For example, an engine of a motorcycle disclosed in Patent Literature 1 includes an oil pump which is mechanically activated by a crankshaft, and oil discharged from this oil pump flows through an oil filter and an oil cooler and then is fed to a main passage in a crankcase. Then, the oil is fed to a valve operating system, a piston, a crank journal, and the like of the engine, through the main passage. The oil is also fed to a transmission via a transmission oil passage.